The present invention relates to hydroxy-substituted azetidinones useful as hypocholesterolemic agents in the treatment prevention of atherosclerosis, and to the combination of a hydroxy-substituted azetidinone of this invention and a cholesterol bioxynthesis inhibitor for the treatment and prevention of atherosclerosis. The invention also relates to a process for preparing hydroxy-substituted azetidinones.
Atherosclerotic coronary heart disease (CHD) represents the major cause for death and cardiovascular morbidity in the western world. Risk factors for atherosclerotic coronary heart disease include hypertension, diabetes mellitus, family history, male gender, cigar smoke and serum cholesterol. A total cholesterol level in excess of 225-250 mg/dl is associated with significant elevation of risk of CHD.
Cholesteryl esters are a major component of atherosclerotic lesions and the major storage form of cholesterol in arterial wall cells. Formation of cholesteryl esters is also a key step in the intestinal absorption of dietary cholesterol. Thus, inhibition of cholesteryl ester formation and reduction of serum cholesterol is likely to inhibit the progression of atherosclerotic lesion formation, decrease the accumulation of cholesteryl esters in the arterial wall, and block the intestinal absorption of dietary cholesterol.
A few azetidinones have been reported as being useful lowering cholesterol and/or in inhibiting the formation of cholesterol-containing lesions in mammalian arterial walls. U.S. Pat. No. 4,983,597 discloses N-sulfonyl-2-azetidinones as anticholesterolemic agents and Ram, et al., in Indian J. Chem., Sect. B. 29B, 12 (1990), p. 1134-7, disclose ethyl 4-(2-oxoazetidin-4-yl)phenoxy-alkanoates as hypolipidemic agents. European Patent Publication 264,231 discloses 1-substituted-4-phenyl-3-(2-oxo-alkylidene)-2-azetidinones as blood platelet aggregation inhibitors. European Patent 199,630 and European Patent Application 337,549 disclose elastase inhibitory substituted azetidinones said to be useful treating inflammatory conditions resulting in tissue destruction which are associated with various disease states, e.g. atherosclerosis.
WO93/102048, published Feb. 4, 1993, discloses substituted xcex2-lactams useful as hypocholesterolemic agents.
The regulation of whole-body cholesterol homeostasis in humans and animals involves the regulation of dietary cholesterol and modulation of cholesterol biosynthesis, bile acid biosynthesis and the catabolism of the cholesterol-containing plasma lipoproteinis. The liver is the major organ responsible for cholesterol biosynthesis and catabolism and for this reason, it is a prime determinant of plasma cholesterol levels. The liver is the site of synthesis and secretion of very low density lipoproteins (VLDL) which are subsequently metabolized to low density lipoproteins (LDL) in the circulation. LDL are the predominant cholesterol-carrying lipoproteins in the plasma and an increase in their concentration is correlated with increased atherosclerosis.
When intestinal cholesterol absorption is reduced, by whatever means, less cholesterol is delivered to the liver. The consequence of this action is decreased hepatic lipoprotein (VLDL), production and an increase in the hepatic clearance of plasma cholesterol, mostly as LDL. Thus, the net effect of inhibiting intestinal cholesterol absorption is a decrease in plasma cholesterol levels.
The inhibition of cholesterol biosynthesis by 3-hydroxy-3-methylglutaryl coenzyme A (HMG CoA) reductase (EC1.1.1.34) inhibitors has been shown to be an effective way to reduce plasma cholesterol (Witzum, Circulation, 80, 5 (1989), p. 1101-1114) and reduce atherosclerosis. Combination therapy of an HMG CoA reductase inhibitor and a bile acid sequestrant has been demonstrated to be more effective in human hyperlipidemic patients than either agent in monotherapy (Illingworth, Drugs, 36 (Suppl. 3) (1988), p. 63-71).
Novel hypocholesterolemic compounds of the present invention are represented by the formula I 
or a pharmaceutically acceptable salt thereof, wherein:
Ar1 and Ar2 are independently selected from the group consisting of aryl and R4-substituted aryl;
Ar3 is aryl or R5-substituted aryl;
X, Y and Z are independently selected from the group consisting of xe2x80x94CH2xe2x80x94, xe2x80x94CH(lower alkyl)xe2x80x94 and xe2x80x94C(dilower alkyl)xe2x80x94;
R and R2 are independently selected from the group consisting of xe2x80x94OR6, xe2x80x94O(CO)R6, xe2x80x94O(CO)OR9 and xe2x80x94O(CO)NR6R7;
R1 and R3 are independently selected from the group consisting of hydrogen, lower alkyl and aryl;
q is 0 or 1; r is 0 or 1; m, n and p are independently 0, 1, 2, 3 or 4; provided that at least one of q and r is 1, and the sum of m, n, p, q are r is 1, 2, 3, 4, 5 or 6; and provided that when p is 0 and r is 1, the sum of m, q and n is 1, 2, 3, 4, or 5;
R4is 1-5 substituents independently selected from the group consisting of lower alkyl, xe2x80x94OR6, xe2x80x94O(CO)R6, R6, xe2x80x94O(CO)OR9, xe2x80x94O(CH2)1-5OR6, xe2x80x94O(CO)NR6R7, xe2x80x94NR6R7, xe2x80x94NR6(CO)R7, xe2x80x94NR6(CO)OR9, xe2x80x94NR6(CO) NR7R8, xe2x80x94NR6SO2R9, xe2x80x94COOR6, xe2x80x94CONR6R7, xe2x80x94COR6, xe2x80x94SO2NR6R7, S(O)0-2R9, xe2x80x94O(CH2)1-10xe2x80x94COOR6, xe2x80x94O(CH2)1-10CONR6R7, xe2x80x94(lower alkylene)COOR6, xe2x80x94CHxe2x95x90CHxe2x80x94COOR6, xe2x80x94CF3, xe2x80x94CN, xe2x80x94NO2 and halogen;
R5 is 1-5 substituents independently selected from the group consisting of xe2x80x94OR6, xe2x80x94O(CO)R6, xe2x80x94O(CO)OR9, xe2x80x94O(CH2)1-5OR6, xe2x80x94O(CO)NR6R7, xe2x80x94NR6R7, xe2x80x94NR6(CO) R7, xe2x80x94NR6(CO)OR9, xe2x80x94NR6(CO)NR7R8, xe2x80x94NR6SO2R9, xe2x80x94COOR6, xe2x80x94CONR6R7, xe2x80x94COR6, xe2x80x94SO2NR6R7, S(O)0-2R9, xe2x80x94O(CH2)1-10xe2x80x94COOR6, xe2x80x94O(CH2)1-10CONR6R7, xe2x80x94(lower alkylene)COOR6 and xe2x80x94CHxe2x95x90CHxe2x80x94COOR6;
R6, R7 and R8 are independently selected from the group consisting of hydrogen, lower alkyl, aryl and aryl-substituted lower alkyl; and
R9 is lower alkyl, aryl or aryl-substituted lower alkyl.
R4 is preferably 1-3 independently selected substituents, and R5 is preferably 1-3 independently selected substituents. Preferred are compounds of formula I wherein Ar1 is phenyl or R4-substituted phenyl, especially (4-R4)-substituted phenyl, Ar2 is preferably phenyl or R4-substituted phenyl, especially (4-R4)-substituted phenyl. Ar3 is preferably R5-substituted phenyl, especially (4-R5)-substituted phenyl. When Ar1 is (4-R4)-substituted phenyl, R4 is preferably a halogen. When Ar2 and Ar3 are R4- and R5-substituted phenyl, respectively, R4 is preferably halogen or xe2x80x94OR6 and R5 is preferably xe2x80x94OR6, wherein R6 is lower alkyl or hydrogen. Especially preferred are compounds wherein each of Ar1 and Ar2 is 4-fluorophenyl and Ar3 is 4-hydroxyphenyl or 4-methoxyphenyl.
X, Y and Z are each preferably xe2x80x94CH2xe2x80x94.R1 and R3 are each preferably hydrogen. R and R2 are preferably xe2x80x94OR6 wherein R6 is hydrogen, or a group readily metabolizable to a hydroxyl (such as xe2x80x94O(CO)R6, xe2x80x94O(CO)OR9 and  xe2x80x94OR6, especially xe2x80x94O(CO)NR6R7, defined above).
The sum of m, n, p, q and r is preferably 2, 3 or 4, more preferably 3. Preferred are compounds wherein m, n and r are each zero, q is 1 and p is 2. Also preferred are compounds wherein p, q and n are each zero, r is 1 and m is 2 or 3. More preferred are compounds wherein m, n and r are each zero, q is 1, p is 2, Z is xe2x80x94CH2 and R is xe2x80x94OR6OR6, especially when R6 is hydrogen. Also more preferred are compounds wherein p, q and n are each zero, r is 1, m is 2, X is xe2x80x94CH2xe2x80x94 and R2 is xe2x80x94OR6, especially when R6 is hydrogen.
Another group of preferred compounds is that wherein Ar1 is phenyl or R4-substituted phenyl, Ar2 is phenyl or R4-substituted phenyl and Ar3 is R5-substituted phenyl. Also preferred are compounds wherein Ar1 is phenyl or R4-substituted phenyl, Ar2 is phenyl or R4-substituted phenyl, Ar3 is R5-substituted phenyl, and the sum of m, n, p, q and r is 2, 3 or 4, more especially 3. More preferred are compounds wherein Ar1 is phenyl or R4-substituted phenyl, Ar2 is phenyl or R4-substituted phenyl Ar3 is R5-substituted phenyl, and wherein m, n and r are each zero, q is 1 and p is 2, or wherein p, q and n are each zero, r is 1 and m is 2 or 3.
This invention also relates to a method of lowering the serum cholesterol level in a mammal in need of such treatment comprising administering an effective amount of a compound of formula I. That is, the use of a compound of the present invention as an hypocholesterolemic agent is also claimed.
In still another aspect, the present invention relates to a pharmaceutical composition comprising a serum cholesterol-lowering effective amount of a compound of formula I in a pharmaceutically acceptable carrier.
The present invention also relates to a method of reducing plasma cholesterol levels, and to a method of treating or preventing atherosclerosis, comprising administering to a mammal in need of such treatment an effective amount of a combination of a hydroxy-substituted azetidinone cholesterol absorption inhibitor of formula I and a cholesterol biosynthesis inhibitor. That is, the present invention relates to the use of a hydroxy-substituted azetidinone cholesterol absorption inhibitor of formula I for combined use with a cholesterol biosynthesis inhibitor (and, similarly, use of a cholesterol biosynthesis inhibitor for combined use with a hydroxy-substituted azetidinone cholesterol absorption inhibitor of formula I) to treat or prevent atherosclerosis or to reduce plasma cholesterol levels.
In yet another aspect, the invention relates to a pharmaceutical composition comprising an effective amount of a hydroxy-substituted azetidinone cholesterol absorption inhibitor of formula I, a cholesterol biosynthesis inhibitor, and a pharmaceutically acceptable carrier. In a final aspect, the invention relates to a kit comprising in one container an effective amount of a hydroxy-substituted azetidinone cholesterol absorption inhibitor of formula I in a pharmaceutically acceptable carrier, and in a separate container, an effective amount of a cholesterol biosynthesis inhibitor in a pharmaceutically acceptable carrier.
In yet another aspect, the invention relates to a process for preparing certain compounds of formula I comprising the steps:
(a) treating with a strong base a lactone of the formula 
wherein Rxe2x80x2 and R2xe2x80x2 are R and R2, respectively, or are suitably protected hydroxy groups; Ar10 is Ar1, a suitably protected hydroxy substituted aryl or a suitably protected amino-substituted aryl; and the remaining variables are as defined above, provided that in lactone of formula B when n and r are each zero, p is 1-4;
(b) reacting the product of step (a) with an imine of the formula 
wherein Ar20 is Ar2, a suitably protected hydroxy-substituted aryl or a suitably protected amino-substituted aryl; and Ar30 is Ar3, a suitably protected hydroxy-substituted aryl or a suitably protected amino-substituted aryl;
c) quenching the reaction with an acid;
d) optionally removing the protecting groups from Rxe2x80x2, R2xe2x80x2, Ar10, Ar20 and Ar30, when present; and
e) optionally functionalizing hydroxy or amino substituents at R, R2, Ar1, Ar2 and Ar3.
Using the lactones shown above, compounds of formula IA and IB are obtained as follows: 
wherein the variables are as defined above; and 
wherein the variables are as defined above.